LayoutLib: Misc fixes.

- Fix resource resolution for framework
  resources of type "id" that are dynamically generated
  through "@+id/..."

- Proper implementation of setBitmap on a canvas that
  already has a bitmap. Transform/clip are kepts but the
  existing layers are replaced with the new bitmap

- return a null service for INPUT_METHOD_SERVICE in
  Context.getSystemService

Change-Id: I35e46fff50e6492a8995e95427d5f38bc945429d